Champa kings. Thanks to this marriage, Đại Việt acquired lands (as dowry) of what is now Quảng Trị Province, and Thừa Thiên-Huế Province (provinces which were then known respectively as Chau O and Chau Ri or Chau Ly).
During the time of the Trịnh-Nguyễn War (1558–1775), Vietnam was divided into two countries: Dang Trong (South) and Dang Ngoai (North) with the Gianh Riveras frontier line. Đồng Hới was an important fortress of the southern Nguyễn Lords. The Đồng Hới Wall ới) was considered the barrier which protected the Nguyễn Lords from the attack by northern Trịnhfamily. During the Indochina War (between the French and the Viet Minh in 1950s), the Đồng Hới airbase was used by the French to attack both the Viet Minh in north-central Vietnam and the Laotian Pathet Lao Army in central and southern Laos. During the Vietnam War, Đồng Hới was heavily devastated by bombardments from the United States B-52 due to its location near seventeenth parallel and the Demilitarized Zone between North Vietnam and South Vietnam.
On 19 April 1972, during a major North Vietnam offensive, a task force of four US ships was sailing off the coast of Vietnam. They were the USS Oklahoma City, USS Sterett, the USS Lloyd Thomas and the USS Higbee. They were attacked by three North Vietnamese MiGs in an attack known as battle of Đồng Hới. In an attempt to surprise the task force, the MiGs came in low, described as getting their feet wet. Despite the official stories, they did not surprise the task force, which had spotted them long before engagement range and were ready to shoot. Two ships, the Oklahoma City, and the Sterett, had anti-aircraft missiles, while the Higbee and the Lloyd Thomas were armed with dual purpose 5" guns. All ships were at battle stations. This city is also the narrowest land of Vietnam (around 40 km from the east to the west) After the fall of Saigon on 30 April 1975, Quảng Bình province was merged
